Integrated circuit (IC) devices are prone to electrostatic discharge (ESD) events, whereby external contacts of the IC devices are subjected to large electrical charges (positive or negative). Functional circuitry within an IC device is required to be protected from electrical currents created by such large electrical charges at the external contacts of the IC devices, which can cause erroneous behavior within the functional circuitry and even permanently damage the functional circuity due to the magnitude of the electrical currents that can be generated by ESD events.
To protect the functional circuitry of an IC device from ESD events, it is known to provide susceptible external contacts of the IC device with ESD protection structures. Conventional ESD protection structures typically include thyristor structures (i.e. P-N-P-N semiconductor structures) coupled between an external contact to be protected, such as an input/output (I/O) contact of the IC device, and a power supply contact (e.g. ground or Vss) to which ESD currents are to be shunted.
Silicon on insulator (SOI) technology refers to the use of a layered silicon-insulator-silicon substrate in place of conventional silicon substrates in semiconductor manufacturing, especially microelectronics, to reduce parasitic device capacitance, thereby improving performance. SOI-based devices differ from conventional silicon-built devices in that the silicon junction is above an electrical insulator such as silicon dioxide. The implementation of SOI technology is one of several manufacturing strategies employed to allow the continued miniaturization of microelectronic devices. However, the footprint of ESD protection structures at the external contacts of such devices is a significant limiting factor in the minimum size of IC device that can be achieved.
Furthermore, conventional ESD protection structures have been found to have poor robustness against ESD gun stress tests when implemented with SOI technology due to current focalization causing hotspots within the ESD protection structures, and often do not meet ESD requirements for automotive applications and the like, for example the 150 pF/330Ω or 2 kΩ/330 pF gun model and the required +/−8 kV gun stress target.